This invention relates to a fine or precise rotation mechanism for rotating, with high precision, an object to a desired position.
Recently, an electron beam drawing system, a reduction projection type transfer system and an X-ray lithography system have been developed as systems for forming a fine pattern on an object such as a semiconductor wafer and a mask substrate. This type of apparatus requires a driving mechanism for slightly and precisely moving a sample on the order of submicrons. High precision, fine driving mechanisms are required not only for the systems mentioned above, but also in technical fields where precise measurements are required.
Fine driving mechanisms include those in which an object is moved linearly in one direction and those in which an object is rotated. The prior art fine rotation mechanisms for causing a rotating motion have the following problems. With a driving mechanism where the rotating stroke is large, it is difficult to obtain slight motion. On the other hand, with a driving mechanism where slight motion is possible, it is impossible to provide a large rotating stroke.
A fine rotation mechanism which solves the above problem was proposed by the inventor of the present application in U.S. Pat. No. 4,455,501 issued on June 19, 1984. However, even in this fine rotation mechanism, the following problem is presented. Rotational driving members, i.e., piezoelectric elements which can be elongated and contracted according to the voltage applied to them, are arranged on a rotating table, and high voltage lines are connected to the rotational driving members to drive them. In principle, in this fine rotation mechanism, the rotating table can be rotated at any speed. However, every time the rotating table revolves, the lines are twisted, and the rotating table can be rotated only by a predetermined number of revolutions. In addition to this disadvantage, the lines are brought into slidable contact with fixed members to be damaged thereby, resulting in incomplete electric insulation.